Field of the Invention
The present invention relates to an image reading apparatus with a reading position determination unit that determines a reading position for an original.
Description of the Related Art
There is conventionally known an image reading position apparatus which conveys originals mounted on an original tray one by one using an automatic document feeder (ADF), irradiates an original at a reading position with light from a light source, and causes reflected light to fall on image pickup devices such as CCDs to read an image off the original.
In the image reading apparatus with the ADF, smudges may adhere to a reading glass above a reading position due to sheet powder of an original itself which is being conveyed or coming-off of toners printed on the original. When an original is read while being moved with smudges such as sheet powder or toners adhered to the reading glass, light that irradiates a surface of the original is blocked by the smudges, and hence vertical streaks may appear in the read image at positions corresponding to places to which the smudges are adhered. Thus, in the image reading apparatus that reads an image off an original while conveying the original, it is preferred that a position on the reading glass at which there is no smudge is determined as an original reading position, and the original is read at this original reading position.
For image reading apparatuses having a reading position determination unit, there has been proposed a technique that, in a reading position setting mode, detects the presence or absence of smudges in an image which has been read at a predetermined reading position, and when it is judged that there are smudges, changes a reading position to detect the presence or absence of smudges again (see Japanese Laid-Open Patent Publication (Kokai) No. 2004-179818 and U.S. Pat. No. 6,563,938). When it is judged that there is no smudge in an image read at the changed reading position, an image is read off an original at this reading position.
However, according to the technique described above, a position on the reading glass at which there is no smudge is determined as a reading position, and this raises a problem that when, for example, smudges are not completely avoided due to the reading glass being too dirty, an image cannot be read in a satisfactory manner.